Industrial furnaces are used in many applications from boilers to cracking furnaces. A broad range of fuels are burned in such furnaces for example from bunker oil to natural gas enriched with hydrogen. With an increase in the cost of petrochemical fuels and a heightened awareness of emissions one would have thought that the application of microprocessors would be applied to furnace combustion in general and combustion at one or a number of burners. A significant amount of art in this field has not been located.
U.S. Pat. No. 4,749,122 issued Jun. 7, 1988 to Shriver et al. assigned to the Foxboro Company relates to a combustion control system. The fuel appears to be low cost solid fuel and the “combustion device” appears to be a grating. The patent does not seem to refer to multiple fluid fired burners. The patent teaches to control oxygen to fuel ratios based on the overall heat balance of the furnace.
U.S. Pat. No. 5,261,811, issued Nov. 16, 1993 to Bae, assigned to SamSung Electronics Company Ltd., teaches regulating the flow of fuel and oxygen (air) to a burner by balancing the load on the fan supplying air to the burner and the load on the pump for fuel to the burner. The patent does not teach measuring a number of parameter extrinsic to the fuel pump.
U.S. Pat. No. 7,838,297, issued Nov. 23, 2010 to Widmer et al., assigned to General Electric Company, relates to a coal fired power plant. The patent teaches using a grid of sensors selected from the group consisting of unburned carbon or loss on ignition CO sensors, CO2 sensors, NOx sensors, O2 sensors, total hydrocarbon (THC) sensors, volatile organic compound (VOC) sensors, sulphur dioxide (SO2) sensors, heat flux sensors, radiance sensors, opacity sensors, emissivity sensors, moisture sensors, hydroxyl radical (OH) sensors, sulphur trioxide (SO3) sensors, particulate matter sensors, and temperature sensors. The grid is arranged so that the combustion characteristics of each burner may be monitored. In response to “a spatial imbalance” in the furnace, the air flow to one or more burners is adjusted to restore or achieve “spatial uniformity”. However, the identification of the burner acting in an anomalous manner is not done directly. Rather, the patent teaches at col. 4, lines 31 to 35. “Identifying 60 burners responsible for the spatial combustion anomalies includes tracing burners 28 to corresponding sensors. Particularly, tracing the burners can be accomplished by computational flow modeling, isothermal flow modeling, and/or empirically by adjusting individual burner air settings and noting changes to sensor output data.” The present invention is not so much concerned about burner operation but rather minimizing the amount of air required for complete combustion at each burner.
The present invention seeks to provide a furnace having a simple fairly direct method for measuring the performance of one or a group of burners and reducing the amount of excess air/oxygen being fed to the furnace and burners to reduce greenhouse emissions, reduce noxious emissions and to reduce the heat load on the furnace to heat unnecessary air/oxygen.